/Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/MeshRefinerBase.h
Check if edge collapse will create a triangle with small area (either all vertices are close together, or in a sliver configuration) This only checks one-ring of vid, so you have to call it twice, with vid and vother reversed, to check both one-rings
bool CheckIfCollapseCreatesTinyTriangle ( int vid, int vother, const FVector3d & newv, int tc, int td ) const